This invention relates to improvements for rotary knives shearing machines and more particularly a rotating knives dividing shears cutting device, to cut bars which are advancing at a very high speed.
In the prior art, the problem of designing a device for cutting and separating bar stock coming from a rolling mill or some other place and which is advancing at a very high speed, is very well known.
In the prior art, particularly for rolling equipment, the need to develop a device to cut such advancing bar stock is very urgently felt, because there is an obvious need to improve the speed characteristics of such equipment.
It is known, that the basic problem which prevents the increase of the working speed of this type of equipment, is one concerning the crop cutting of the bars and/or their cutting to length, and to separate the advancing bars. This problem is not only related to bar cutting equipment, but also relates to similar equipment such as wire-manufacturing equipment.
The limitation of the maximum speed of the presently used rotary side-trimming shears depends on the fact, that these shearing machines work rhythmically which means that the knives are held firm in a waiting area of non interference with the passage of the bar, and they accelerate on a predetermined signal and with a peripheral speed equal to the one for the advancement of the bar they are to cut. These machines then decelerate and stop again at a dead waiting point, and then start again for a new cut and so on. This solution is based on the actual need to effect the cut of the bar at the chosen moment and at the chosen point. This technique actually employs practically exclusively various types of rotating knives. Other types are not very often in use, because they are too expensive and mostly not very practical.
These first types of rotating knives comprise generally an electric motor connected to a continuously rotating flywheel from which, with the use of a clutch, the motion is immediately transmitted to the rotating knives for the cut, and then with the utilization of a brake they are brought into a waiting position at the said dead point. This may also be achieved with an improved apparatus, including a collateral motor for the replacement of the phase and with a collateral clutch means, as for instance described in the Italian patent application of the same inventor, registered in Italy on Jan. 15, l977, under Nr. 83307 A/77, where among others a particular way of operating is described to establish the dead point immediately downstream of the cutting area.
The present invention provides a solution which employs high speed for the above-mentioned purpose, but with the use of special devices in the areas for acceleration and deceleration of the knives, and consequently for the selection of the dead point between each new cut.
However, it is well known that merely increasing the peripheral speed of the knives has practical limits, depending on the loading caused by violent accelerations and decelerations. Therefore if one intends to increase the speed, the problems associated with the above-described constructive schemes are so difficult as to discourage attempts at building shearing machines of this type with increased speed. The choice for the inventor is therefore based in the first instance on the research for a solution which allows both an increase of the peripheral speed of the knife and more control over the inertia of the rotating mass, even if this requires an increase in power or energy use, for instance because of higher frictions, which would only require an increase for the transmission and a drive motor with very high power. In the second instance the choice for the inventor is based on the research for a solution which achieves an improved cutting operation.